Blog

Ransomware seeks victims via TeamViewer

Download-TeamViewerAnyone use Teamviewer? If so, sorry to say,  you may have been hacked.

A new ransomware has been discovered appending the .surprise extension to encrypt important files. Further research into the extension revealed the loader had EDA2 ransomware from memory, and was only attacking those who also had TeamViewer installed. The victim logs showed that TeamViewer had been utilized as a means to reach computers. Someone connected via TeamViewer and proceeded to download the encrypted surprise files onto the unsuspecting desktop.

The two TeamViewer IDs used by the attackers were  479441239 and 479440875.

This surprise ransomware is unique in that it has successfully bypassed AV signature definitions as well as behavior detection. Rather than containing the more typical encryption functions seen in ransomware, this surprise ransomware encompassed an encrypted BASE64 encoded string. This string is loaded into memory and functions from there.

The ransomware scans all fixed disks on the computer for files that contain a particular file extension. When it finds a matching file, it will encrypt it with the AES encryption key and append the .surprise extention to it. The targeted file extensions are a hefty list. It will skip any files containing the $ symbol or contain the c:/windows and c:/program strings in the filename.

Bleeping Computer discovered the 3 files the ransomware creates are as follows:

  • %Desktop%\DECRYPTION_HOWTO.Notepad ransom note.
  • %Desktop%\surprise.bat, which¬†executes the vssadmin.exe Delete Shadows /All /Quiet to remove Shadow Volume Copies.
  • %Desktop%\Encrypted_Files.Notepad¬†file that¬†contains a list of encrypted files

Sadly for those encrypted there is no alternative method to gain access to the files at this time without paying the ransom.

If you would like to educate yourself in greater detail about the material presented in this blog post please visit:

http://www.bleepingcomputer.com/news/security/surprise-ransomware-installed-via-teamviewer-and-executes-from-memory/